The soil sampler is the simplest way to see how much moisture your mirliton roots are getting. It’s the only quick, inexpensive way to see if you have over-watered or underwater your vine. James Leblanc shows you how to take a sample and check the moisture levels at root zone levels.
See the video here
Buy a soil sampler here.
How to use appearance and feel to estimate soil moisture:
https://nutrientmanagement.tamu.edu/content/tools/estimatingsoilmoisture.pdf
Mirliton roots extend 12″ deep: